As will be apparent from Swedish Patent Nos. 503,010 and 509,519, such press rolls are at present sealed by means of an end seal that connects with the end surface of the roll, wherein a longitudinally extending seal in the form of a flexible element is pressed against the cylindrical surface of the roll.
It is generally difficult to seal around a corner of a rotating press roll, because the roll is moveable in two directions. Firstly, the roll moves axially as a result of thermal expansion, and secondly it moves radially as a result of variation in the clearance between rolls. Sealing against the roll end is achieved with the end seal and with the seal that extends longitudinally along the roll, both of these seals being pressurised and “floating” with the roll in a direction that is normal to the sealing surface. Sealing around the corner of a roll is effected with the aid of a static seal that seals against the longitudinally extending seal on the one hand and against the end seal on the other hand.
The static seal tends not to follow the sealing surface, and is therefore mounted with a given clearance in relation thereto. This clearance can result in leakage if excessively large and in wear of the sealing surface if excessively small.
One object of the present invention is to provide a seal at an edge of a moveable roll that will solve the aforesaid problems, and then in particular with regard to a roll of a roll press for de-watering material suspensions.